<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <meta http-equiv="X-UA-Compatible" content="ie=edge" />
  <title>定位 </title>
  <style>
    .content {
      width: 1000px;
      height: auto ;  
      position: relative;
      margin: 15px auto;
      
    }

    .totop {
      position: fixed;
      right: 0px;
      bottom: 40px;
      width: 60px;
      height: 60px;
      background-color: #ccc;
      border-radius: 5px;
      overflow: hidden;
      cursor: pointer;
    
    }

  

    .totop img {
    position: relative;
     left: -195px;
    top: -100px;
    transition: all ;
    }

    .totop:hover img {
    left: -103px;
    top: -285px;
    }
    
    .side-img {
      width: 120px;
      height: auto;
    }


    .left-img {
      position: fixed;
      left: 0;
      top: 50%;
      margin-top: -100px;
    }

    .right-img {
      position: fixed;
      right: 0;
      top: 50%;
      margin-top: -100px;
      
    }

    
  </style>
</head>
<body>

  <a id="top"></a>
  <img src="./img/ad-l.png" class="left-img side-img"  />
  <img src="./img/ad-r.png" class="right-img side-img"  />
  <div class="content">
    <img src="./img/box.png" />
  </div>
  <a href="#top" class="totop">
    <img src="./img/sprite_right.png" />
  </a>
</body>
</html>
